Numerical Calculations of Heat Conduction Between Soot Aggregates and the Surrounding Gas in the Free-Molecular Regime Using the DSMC Method

2005 ◽  
Author(s):  
Fengshan Liu ◽  
Min Yang ◽  
David R. Snelling ◽  
Gregory J. Smallwood
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Direct Simulation Monte Carlo ◽  
Interaction Model ◽  
Numerical Calculations ◽  
Hard Sphere Model ◽  
Sphere Diameter ◽  
Free Molecular Regime ◽  
Thermal Accommodation ◽  
Maxwell Gas

Numerical calculations were conducted to calculate the heat conduction rate between soot (carbon) aggregates of different sizes and the surrounding gas in the free-molecular regime using the direct simulation Monte Carlo method. This method is based on simulation of the trajectories of individual molecules and calculation of the heat transfer at each of the molecule/molecule collisions and the molecule/particle collisions. Soot aggregates of known fractal dimension and pre-factor are first numerically generated using a cluster-cluster aggregation algorithm. Effect of incomplete thermal accommodation was accounted for by employing the Maxwell gas-surface interaction model. Gas collisions were treated using the simple hard sphere model. Numerical results were obtained for aggregate sizes between 10 and 228 primary particles and the thermal accommodation coefficient between 0.1 and 1. A simple scaling for the heat transfer equivalent sphere diameter was also presented for incorporation into a laser-induced incandescence model.

Theoretical Two-Dimensional Modeling of Gas Conduction Between Finite Parallel Plates in High Vacuum

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Taishan Zhu ◽  
Wenjing Ye
Keyword(s):  
Heat Transfer ◽  
High Vacuum ◽  
Finite Size ◽  
Direct Simulation Monte Carlo ◽  
Free Molecule ◽  
Mems Devices ◽  
Parallel Plates ◽  
Thermal Accommodation ◽  
Representative Model ◽  
Gas Conduction

A theoretical approach based on gaskinetic theory is described and applied for the modeling of steady-state free-molecule gaseous heat conduction within a diffusive enclosure. With a representative model of microelectromechanical system (MEMS) devices with integrated heaters, the heat transfer between the heated component and its gaseous ambient enclosed in a high vacuum is studied in detail. A molecular simulation based on the direct simulation Monte Carlo (DSMC) method is also employed to validate the theoretical solutions and to study the effects of incomplete thermal accommodation. The impacts of the finite size of the heated beam as well as the gap between the beam and a substrate on the heat transfer are investigated to examine the appropriateness of the common assumptions employed in the modeling of Pirani sensors. Interesting phenomena that are unique in the free-molecule regime are observed and discussed. These studies are valuable to the design of MEMS devices with microheaters.

Heat Conduction From Circular Cylinders in Rarefied Gases

1965 ◽  
Vol 87 (4) ◽  
pp. 493-498 ◽  
Author(s):  
G. S. Springer ◽  
R. Ratonyi
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Transition Temperature ◽  
Cylindrical Surface ◽  
Temperature Jump ◽  
Circular Cylinders ◽  
Conductive Heat ◽  
Free Molecule ◽  
Thermal Accommodation ◽  
Concentric Cylinders

A method is presented for calculating the conductive heat transfer through gases contained between two concentric cylinders. The method of Lees and Liu is extended to include incomplete thermal accommodation at the inner cylindrical surface, and a comparison is made between the two methods. These results are then compared to those of the low pressure and temperature jump methods. On the basis of this analysis, limits are obtained for the free-molecule, transition, temperature jump, and continuum regimes.

Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry

2018 ◽  
Author(s):  
Dilesh Maharjan ◽  
Mustafa Hadj-Nacer ◽  
Miles Greiner ◽  
Stefan K. Stefanov
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas ◽  
Complex Geometry ◽  
Direct Simulation Monte Carlo ◽  
Accurate Method ◽  
Vacuum Drying ◽  
Helium Pressure ◽  
Two Dimensional ◽  
Dsmc Method ◽  
Cfd Simulations

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

scholarly journals The Single-Blow Problem Including the Effects of Longitudinal Conduction

1964 ◽  
Author(s):  
C. P. Howard
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Conduction ◽  
Transient Behavior ◽  
Step Change ◽  
Graphical Form ◽  
Compact Heat Exchanger ◽  
Fluid Temperature ◽  
Transfer Data ◽  
Method Of Calculation

The results are presented from a numerical finite-difference method of calculation for the transient behavior of porous media when subjected to a step change in fluid temperature considering the case where the longitudinal thermal heat conduction cannot be neglected. These results, given in tabular and graphical form, provide a useful means for evaluating the heat-transfer data obtained from the transient testing of compact heat-exchanger surfaces.

Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms

2015 ◽  
Vol 17 (25) ◽  
pp. 16476-16482 ◽  
Author(s):  
Liu Cui ◽  
Yanhui Feng ◽  
Peng Tan ◽  
Xinxin Zhang
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Heat Conduction ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Reduction Mechanisms ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Theoretical insights into the heat transfer performance and its reduction mechanisms in double-walled carbon nanotubes with intertube additional carbon atoms.

A Thermal Model to Predict Tool Temperature in Machining of Ti-6Al-4V Alloy With an Atomization-Based Cutting Fluid Spray System

2016 ◽  
Author(s):  
Asif Tanveer ◽  
Deepak Marla ◽  
Shiv G. Kapoor
Keyword(s):  
Heat Transfer ◽  
Interaction Model ◽  
Spray Cooling ◽  
Droplet Surface ◽  
Cutting Fluid ◽  
Design Parameters ◽  
Transfer Model ◽  
Tool Temperature ◽  
Spray System ◽  
Heat Transfer Phenomenon

In this study a heat transfer model of machining of Ti-6Al-4V under the application of atomization-based cutting fluid spray coolant is developed to predict the temperature of the cutting tool. Owing to high tool temperature involved in machining of Ti-6Al-4V, the model considers film boiling as the major heat transfer phenomenon. In addition, the design parameters of the spray for effective cooling during machining are derived based on droplet-surface interaction model. Machining experiments are conducted and the temperatures are recorded using the inserted thermocouple technique. The experimental data are compared with the model predictions. The temperature field obtained is comparable to the experimental results, confirming that the model predicts tool temperature during machining with ACF spray cooling satisfactorily.

Computations of Low Pressure Fluid Flow and Heat Transfer in Ducts Using Direct Simulation Monte Carlo Method

1999 ◽  
Author(s):  
Fang Yan ◽  
Bakhtier Farouk
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Noble Gas ◽  
Direct Simulation Monte Carlo ◽  
Low Pressure ◽  
Direct Simulation ◽  
Flow And Heat Transfer ◽  
Gas Transport Properties ◽  
Pressure Profiles ◽  
Simulation Monte Carlo

Abstract High Knudsen (Kn) number flows are found in vacuum and micro-scale systems. Such flows are characterized by non-continuum behavior. For gases, the flows are usually in the slip or transition regimes. In this paper, the direct simulation Monte Carlo (DSMC) method has been applied to compute low pressure, high Kn flow fields in partially heated channels. Computations were carried out for nitrogen, argon, hydrogen, oxygen and noble gas mixtures. Variation of the Kn is obtained by reducing the pressure while keeping the channel width constant. Nonlinear pressure profiles along the channel centerline are observed. Heat transfer from the channel walls is also calculated and compared with the Graetz solution. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nu) were examined. A simplified correlation for predicting Nu¯ as a function of Pe¯ and Kn¯ is presented.

Sign in / Sign up

Export Citation Format

Share Document